All known natural calcitonin peptides contain an amino acid sequence of 32 amino acids. Salmon calcitonin, for example, has the following formula: ##STR1##
In U.S. Pat. Nos. 3,926,938, 4,062,815, 3,929,758, 4,033,940 and 4,217,268 are disclosed improved syntheses of calcitonins including the salmon calcitonin above referred to.
The natural calcitonins include the salmon calcitonins, bovine, porcine, ovine, and eel calcitonins and human calcitonins. All of these have leucine at position number 16 except human calcitonin which has phenylalanine at position number 16.